1

Running Cadence

Once the Cadence environment has been setup you can start working with Cadence. You

can run cadence from your directory by typing

Figure 1.

Main window (Common Interface Window), CIW opens and from the pull down menus

you can start your design.

Figure 2.

To create your own library, select from File-> New -> Library, the pop-up window

shows up as shown in the Figure 3.

2

Figure 3.

In the Name section write the name of library. You need add a technology file to your

new library. You can attached or compile a tech file to the library. In this case you will

attach an existing tech. file. You can attach the technology file from the “gpdk” library as

shown in the Figure 4.

Figure 4.

After creating the working library, you can start creating various views to simulate your

design.

3

I-V Characteristics of Diode

First we start by creating the new cell view for the diode. From File-> New -> Cellview

Figure 5.

This creates the schematic view as shown in the Figure 5. You will be using a voltage

supply, resistor, and a diode to create the schematic view as shown in the Figure 6.

Figure 6.

4

To add any of the components in the schematic:

From Add-> Instance ->

Figure 7.

Select the diode, voltage supply, resistance and ground as shown in the Figures 7, 8, 9

and 10.

5

Figure 8.

6

Figure 9.

Figure 10.

7

Place the components as shown in the Figure 6. At this point you are ready to start the

simulation.

From Tools-> Analog Environment

Figure 11.

Write the path for the model libraries

Figure 12.

8

Choose dc type of analysis from Analysis -> Choose

Figure 13.

9

Variables to be plotted are selected from the schematic

Figure 14.

To plot voltages select the wire, and to plot current select the red square nodes or select

on the component. Figure 15 shows how the selected voltages and current nodes look

line after being selected for simulation.

Figure 15.

10

Now we are ready to perform simulation. After clicking on Simulation-> Netlist and Run

simulation starts.

Figure 16, shows the spectre output log file that gets generated for simulation.

Figure 16.

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The waveform created looks like :

Figure 17

To display Current (I) versus Voltage (V) we start by setting the axis.

From Axis-> X Axis

Figure 18.

12

Change the X axis to be the voltage drop on the diode or /net5 voltage as shown in the

Figure 19.

Figure 19.

After changing the X axis, the waveform looks like, as shown in Figure 20:

Figure 20.

13

Because we are interested only on the I-V plot for the current and voltage of the diode,

we can select only the D1/PLUS current node and /net5 voltage drop of the diode. The

new waveform will look like shown in Figure 21.

Figure 21.

14

I-V Characteristics of BJT

Initially start a new schematic cellview for the bjt circuit. Figure 22, displays the circuit

used for simulation. After adding all the necessary components, connect them together

and the last part is editing the variables.

The power supply “vdc” is identified with a variable voltage “VBB”. You can do this by

editing the properties of the power supply.

Figure 22.

After complting the schematic, we are ready to start simulation.

From Tools -> Analog Enviroment, and the pop-up window as in Figure 23 shows up.

15

Figure 23.

Setting the Variables

Figure 24.

16

Setting the type of Analysis

Figure 25.

After completing these steps you can start simulation by clicking on

Simulation-> Netlist and Run.

At this point you can see the spectre output log file that is created.

After this point you will perform parametric analysis as shown in Figure 26, to view

multiple curves in a single waveform.

17

Figure 26.

Go to Analysis -> Start in the Parametric Analysis window. When the simulation is

complete go to Results -> Direct Plot -> DC and then click on the terminal of the V1

supply, then hit ESC. Now you should again get a nice family of IV curves as shown in

Figure 27.

Figure 27.

18

Generating C-V Plots for MOS Capacitor Device

Figure 28.

19

Figure 29.

20

Figure 30.

21

Figure 31

Perform simulation from Simulation -> Netlist and Run

Figure 32

Then perform Parametric Analysis

Figure 33

22

Figure 34

Parametric Analysis Form

Select output to be displayed: From Output -> Setup

Figure 35

The Form will look like:

Figure 36

23

By clicking on “Open” , the Calculator will open

Figure 37

By clicking on “ OP” and then selecting the device from the schematic view, you will

see a list of variables

Figure 38

24

Figure 39

25

After selecting the variables to be plot, then just click on ERPLOT in the Calculator to

plot.

Figure 39

The waveform will look like:

26

Figure 40

27

Figure 41

28

Variation of the Bandgap Reference Voltage with respect to Temperature

The example below is the classical Widlar Bandgap Voltage Reference

Figure 42

29

By clicking on Tools -> Analog Environment

Figure 43.

The type of analysis is dc as in Figure 44.

30

Figure 44

31

The output signals to be observed during the simulation are:

Figure 45

To start simulation from click on “Netlist and Run”

Figure 46

32

The waveforms for the output signals as we perform dc analysis on variable temperature:

Figure 47

33

Bandgap Temperature Reference (Version 2)

Figure 48

34

Figure 49

35

Figure 50

36

Single Stage Amplifiers

Figure 51

This is a common-source single-transistor amplifier.

37

Type of analysis performed:

Figure 52

38

There are two voltage variables set in this circuit. One is for the VDD voltage and the

other is for Vin source.

Figure 53

The output selected is as highlighted below:

Figure 54

39

This is the waveform obtained form the common-source amplifier.

This waveform plots the output versus the VDD range as Vin is varying from 0->2V.

This waveform plots the Vin vs Vout as VDD varies.

Figure 55 and 56

40

MOS Differential Amplifier with a Current Mirror Load

Figure 57

This is a MOS current mirror load differential amplifier.

41

The type of analysis performed is DC.

Figure 58

42

The analysis is performed on Variable V2 which is the input voltage.

Figure 59

43

The variables used for this simulation are:

Figure 60

Where V1 is for the input voltage and V2 is for the VDD voltage source. Check

schematic for more information.

The parametric analysis performed for variable V1 after performing Dc simulation.

Figure 61

44

The waveform obtained looks like below.

This waveform is Vin vs Vout plot.

Figure 62

45

High Frequency Response in Diff. Pairs

In order to estimate the frequency response of the differential pair with active current

mirror the schematic model shown below is used where all capacitances are neglected.

Figure 63

46

Performing Transient Analysis: The selected nets are input and output nets.

Figure 64

Transient analysis is performed.

47

Figure 65

The waveforms obtained are: Figure 66

48

Noise in Differential Pairs

Figure 67

This type of modeling accounts for 1/f noise and input-referred noise.

49

Performing Transient Analysis: Nets selected are input and output nets.

Figure 68

Transient Analysis

Figure 69

50

The waveforms obtained;

Figure 70